Apparatus for generating and deflecting a plasma jet

ABSTRACT

A plasma jet generator apparatus enabling effective deflection of the generated plasma jet is described. The apparatus has an electrode chamber having a gas inlet and an outlet and an electrode positioned therein defining an electrode axis. A pair of magnetic deflection systems for deflecting the direction of the plasma flowing from the electrode axis are provided. The magnetic deflection systems are formed from pole pairs which are distributed about the electrode axis such that two magnetic fields that are substantially perpendicular to each other can be generated to deflect the plasma away from the electrode axis.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the National Stage of International Application No.PCT/US97/09252, filed on May 30, 1997, which claims the benefit ofprevious co-pending U.S. Provisional Application Ser. No. 60/018,857,filed on May 31, 1996.

BACKGROUND

1. Field of the Invention

The present invention relates to the plasma processing of substrates.More particularly, the present invention relates to an apparatus forgenerating and deflecting a plasma jet for treating substrates using aplasma jet treatment process.

2. Description of the Prior Art

Published application No. PCT/SU90/00286 describes a method for plasmaprocessing of a material consisting of a system of more than two meetingplasma jets which form a mixing zone wherein a material to be processedis fed into the mixing zone. Direct electric currents are passed throughsections of the plasma jets up to the mixing zone and a magnetic fieldis applied to the current conducting sections of each plasma jet. Theapparatus for plasma processing of material described in the applicationcomprises a charge conduit, an electric arc plasma jet generator furthercomprising a plurality of electrode units for generating the plasmajets. The electrode units are oriented at acute angles to an axis of thecharge conduit and are connected to a direct current source. Theapparatus further comprises a magnetic system formed from an openmagnetic circuit with poles located in a mixing zone of the plasma jets.The apparatus described in PCT/SU90/00286 has very limited abilities tocontrol direction of each plasma jet independently so as to control thestructure of combined plasma flow.

Published application No. PCT/SU90/00287 describes an apparatus forplasma-arc processing of material. The apparatus comprises a chargeconduit which is surrounded by a plurality of electric arc plasma jetgenerators and a magnetic system. The generators comprise two electrodeassemblies. Solenoids are mounted on poles of the magnetic circuit. Theapparatus can be used only if the plasma jets are directed towards theaxis of the apparatus with angles more than 45 degrees. If the anglesare less than 45 degrees then the magnetic system itself causesinstability in each of the plasma jets and the combined plasma flow.Another disadvantage is that each plasma jet orientation can becontrolled only when it is located in equilibrium position within anarrow zone near the corresponding basic plane where both a second andthird magnetic field interacts with it. If the plasma jet is deflectedrelatively far from the basic plane then the effectiveness of thecontrol significantly reduces because only one of these magnetic fieldsinteract with the plasma jet.

In published Russian Patent No. 2032281, a method and apparatus forplasma flow production is described. Plasma jets are formed by anymethod and are directed symmetrically to the axis of a common plasmaflow at an angle less than 45 degrees. Direct current is passed alongeach plasma jet in opposite directions relative to the common axis andexternal magnetic fields are applied to each jet. The 1st magnetic fieldis applied between the axis (4) of each jet and the common axis, whilethe 2nd and 3rd fields are applied to the half-spaces between the axes.Interaction of the magnetic fields and the current in the jet causesdeflection of the jets from their axes (2). The induction of the fieldsare adjusted, to ensure the axis (4) of the jets are parallel to thecommon axis after interaction and the configuration of the externalmagnetic fields is selected to increase the stability of the plasmajets. During random slight displacements of the jets, inductance to oneside increases and decreases to the other side, to ensure return of theaxis of the jet to a direction parallel to the common axis. Thedisadvantage of the above described method and apparatus is that themethod can be realized and correspondingly the device can be used onlyif the plasma jets are directed to the device axis with angles less than45 degrees. If the angles are more than 45 degrees then the magneticsystem itself induces instability of every plasma jet and the combinedplasma flow. Another disadvantage is that each plasma jet orientationcan be controlled only when it is located in an equilibrium positionwithin narrow zone near the corresponding basic plane where both secondand third magnetic fields interact with it. If the plasma jet isdeflected relatively far from the basic plane, then the effectiveness ofthe control significantly reduces because of only one of these magneticfields interacts with the plasma jet.

Russian patent document RU 2059344 discloses a plasma generating deviceincluding electrode units having a magnetic system comprising a pair ofU-shaped members or poles and a solenoid. The ends of the poles arelocated in the space defined by the symmetrical planes intersecting theaxis of symmetry of the device. However, the poles are not arranged in amanner to provide perpendicular magnetic fields for steering the plasma.

SUMMARY OF THE INVENTION

The apparatus of the present invention enables effective deflection ofthe direction of a plasma jet. The apparatus for generating anddeflecting the plasma jet comprises an electrode chamber having a gasinlet and an outlet. An electrode is positioned within the electrodechamber. The electrode defines an electrode axis. The generator isprovided with a first magnetic deflection system for applying a firstmagnetic field to a plasma flowing from the electrode chamber outlet soas to cause the plasma to deflect away from the electrode axis in afirst direction relative to the electrode axis. The first magneticdeflection system comprises a first U-shaped member formed from a firstbase and a pair of first poles having ends and a first coil positionedabout the base. The first magnetic deflection system is positioned aboutthe electrode chamber so that the poles are on opposite sides of theelectrode axis defined by the electrode positioned within the electrodechamber. The generator is also provided with a second magneticdeflection system for applying a second magnetic field to the plasmaflowing from the electrode chamber outlet so as to cause the plasma todeflect away from the electrode axis in a second direction relative tothe electrode axis. The second magnetic deflection system comprises asecond U-shaped member formed from a second base and a pair of secondpoles having ends and a coil positioned about the base. The secondmagnetic deflection system is positioned about the electrode chamber sothat the poles of the second pair are on opposite sides of the electrodeaxis defined by the electrode positioned within the electrode chamber.The second pair of poles is further positioned so that all of the polesof the system are uniformly distributed around the electrode axis and sothat the first and second magnetic fields are substantiallyperpendicular to each other. The first and second magnetic deflectionsystems enable the plasma jet to be deflected away from the electrodeaxis in substantially any direction.

One object of the present invention is to provide an apparatus forgenerating a plasma jet and obtaining effective deflection of thegenerated plasma jet flowing from the apparatus.

The foregoing and other objects, features, and advantages will becomeapparent from the detailed description of the preferred embodimentsinvention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings, which are not drawn to scale, include:

FIG. 1, which is a schematic side view diagram of one embodiment of theapparatus of the present invention having two plasma jet generatorassemblies;

FIG. 2, which is a schematic top view diagram of the embodimentillustrated in FIG. 1;

FIG. 3, which is a schematic top view diagram of another embodiment ofthe apparatus of the present invention incorporating two plasma jetgenerator assemblies made in accordance with the present invention;

FIG. 4, which is a schematic top view diagram of still anotherembodiment of the present invention;

FIG. 5, which is a side view partial schematic diagram of the apparatusof the present invention illustrating the positioning of a plasma jetgenerator relative to a common axis;

FIG. 6, which is a schematic to view diagram of another embodiment ofthe present invention;

FIGS. 7 and 8, which are schematic diagrams of the magnetic fields; and

FIG. 9, which is a schematic top view diagram of an electrode assemblyutilized in all the embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the apparatus for producing a flow of plasmacomprises a plurality of plasma jet generator assemblies 5. Referring toFIGS. 1 and 9, each plasma jet generator assembly 5 is formed from anelectrically isolated closed electrode chamber 10 having a base 30 withoutlet orifice 40, gas inlet 50 and an electrode 60 positioned withinthe chamber 10 having an end seated in a dielectric gasket 70. Theelectrode 60 forms an electrode axis 80 which extends out of the orifice40.

Referring to FIGS. 1, 7, 8 and 9, each plasma generator 5 is capable ofgenerating and deflecting a plasma jet. Each generator 5 is providedwith a first magnetic deflection system for applying a first magneticfield B₁ to a plasma flowing from the electrode chamber outlet so as tocause the plasma to flow away from the electrode axis in a firstdirection as a result of a first force F₁ on the plasma caused by thefirst magnetic field. The first magnetic deflection system comprises afirst U-shaped member formed from a first base 110 and a pair of firstpoles 130 having ends 135 and a first coil 120 positioned about thebase. The first magnetic deflection system is positioned about theelectrode chamber so that the poles of the pair of first poles 130 areon opposite sides of the electrode axis defined by the electrodepositioned within the electrode chamber. The generator is provided witha second magnetic deflection system for applying a second magnetic fieldto a plasma flowing from the electrode chamber outlet so as to cause theplasma to flow away from the electrode axis in a second direction as aresult of a second force (F2) on the plasma caused by the secondmagnetic field B₂. The second magnetic deflection system comprises asecond U-shaped member formed from a second base 110 and a pair ofsecond poles 130 having ends 135 and a coil 120 positioned about thebase. The second magnetic deflection system is positioned about theelectrode chamber so that the poles of the pair of second poles are onopposite sides of the electrode axis defined by the electrode positionedwithin the electrode chamber. The first pair of poles and the secondpair of poles are uniformly positioned about the electrode axis and sothat the magnetic field across the first pair of poles is substantiallyperpendicular to the magnetic field across the pair of second poles.

In the apparatus, a plurality of plasma jet generator assemblies 5 inmultiples of two are used. The plurality of generator assemblies 5 arespatially positioned about an apparatus axis 90 and angularly positionedso that the electrode axis 80 forms angle α with the apparatus axis 90.The angle α is selected to be less than 90 degrees. Referring to FIG. 2,if two generator assemblies 5 are used, the generator assemblies arepositioned on opposite sides of the apparatus axis 90 so that theircorresponding electrode axes 80 and the apparatus axis 90 form a basicplane. Referring to FIG. 3, if four generator assemblies 5 are used,they are positioned around apparatus axis 90 with angle β≅90° betweentheir corresponding basic planes. If more than four generator assemblies5 are used, they are located around the apparatus axis 90 with angleβ≅360°/N between their corresponding basic planes, where N is thequantity of generator assemblies 5. Each of the electrodes 60 of thegenerator assemblies 5 are connected in pairs to a DC power supply 100.

The generator assemblies are provided with the magnetic deflectingsystem as described above. The ends 135 of the poles 130 are positionedaround the electrode axes 80. The ends 135 of each pole 130 are locatedin a plane which is perpendicular to the corresponding electrode axis80. The plane formed by the ends 135 intersects the correspondingelectrode axis 80 at a position in a range between the correspondingelectrode chamber orifice 40 and a point of intersection 175 between theelectrode axis 80 and apparatus axis 90. Each of the pole ends 135 ispositioned from its corresponding electrode axis 80 a distance that ismore than the diameter of the corresponding electrode chamber orifice40. The length of each of the pole ends 135 along its correspondingelectrode axis 80 and the width of each of the pole ends 135 are chosento be greater than the diameter of the corresponding electrode chamberorifice 40. The centers of the pole ends 135 are positioned at differentsides relative to the corresponding basic plane formed thereby.

Referring to FIG. 1, the apparatus may be provided with injection tube150 having an outlet hole 162 at end 160. The tube 150 is affixed in thebase 20 and aligned with apparatus axis 90. The distance between the end160 of the injection tube 150 and the point of intersection 175 of theelectrode unit axes 80 and apparatus axis 90 is chosen to avoid thermaldamage to the end 160 of the injection tube 150 end by heat from theadjacent plasma jets.

Referring to FIG. 4, for design simplification, each of the unclosedmagnetic circuits formed by the U-shaped members may be connected toanother corresponding unclosed magnetic circuit via bridge member 140.Also, referring to FIG. 6, for design simplification, one of the poles130 of one of first unclosed magnetic circuit of one electrode assemblymay be connected with the nearest pole 130 of another unclosed magneticcircuit of the another adjoined electrode assembly. In both cases, themagnetic system has the same main external magnetic field pattern as theseparated magnetic circuits, but the coils' 120 effectiveness is reduceddue to the increase of side-by-side magnetic field losses of the coils.Referring to FIGS. 1 and 2, if the apparatus contains only two generatorassemblies 5, the end 160 of injection tube 150 may be provided with anopening 162 which has a dimension along the basic plane formed by theelectrode axes 80 that is less than the dimension of the electrodechamber orifices 40. Along the direction perpendicular to the basicplane formed by the electrode axes 80, the dimension of the opening 162may be made larger than the dimension along the basic plane. In otherwords, the opening 162 in the tube 150 may have an oval shape whereinthe long axis of the oval is normal or perpendicular to the plane formedby the electrode axes 80.

Referring to FIG. 4, the end 160 of the injection tube 150 may be madewith a plurality of openings 162a-162e. The plurality of openings162a-162e are preferably aligned along the plane normal or perpendicularto the basic plane formed by the electrode axes 80.

Referring to FIG. 1, according to the present invention, gas isdelivered into each electrode chamber 10 through gas inlet 50, in thedirection indicated by arrow A. An electrical arc discharge 170 with DCelectrical current I is ignited between the electrodes 60 of each pairof electrode chambers 10 with the help of DC power supply 100. Thedistance between electrode chambers 10 in every pair and angle α arechosen to provide a stable electrical discharge 170 from DC power supply100.

The gas flowing through the orifices 40 of the chambers 10 andelectrical discharge 170 create plasma jets 180. The plasma jets 180combine in mixing zone 190 to form a combined plasma flow 200. Becauseof the electro magnetic interaction of the electrical currents I in theplasma jets 180, a force F_(S) is applied to each of the plasma jets 180which is directed away from the apparatus axis 90. As a result of theapplication of force F_(S), the plasma jets 180 bend from their initialdirections along electrode axes 80 out towards the apparatus axis 90.

An electrical current is conducted through the coil 120 of everyunclosed magnetic circuit 110. Referring to FIGS. 7 and 8, as a resultof the electrical current flowing through coil 120, an external magneticfield is created between the ends of the poles 130 of each of theunclosed magnetic circuit 110.

Referring to FIG. 7, which looks into the apparatus axis 90, if theelectrode 60 having electrode axis 80 which is directed with an angle αthat is more than 45 degrees with respect to the apparatus axis 90, thenthe directions of electrical current in the coils 120 of both unclosedmagnetic circuits 110 are chosen to provide external magnetic fieldinduction vector components B₁⊥ and B₂⊥ that are directed perpendicularto the basic plane formed by the electrode axes 80 and the apparatusaxis 90, and are oriented along the same direction as the orientation ofthe corresponding plasma jet's 180 self-magnetic field induction vectorB_(S), due to its current I, at the region of the basic plane betweenthe electrode axis 80 and apparatus axis 90. The current I of the upperelectrode and the current I of the lower electrode flow in oppositedirections as illustrated in FIG. 7. The external magnetic fieldinduction vector components B₁⊥ and B₂⊥ create electromagnetic forcesF₁⊥ and F₂⊥ correspondingly that are applied to the plasma jet 180 anddirected away from the apparatus axis 90. The quantity of electricalcurrents flowed through the coils 120 are chosen to provide a sum offorces F₁⊥ and F₂⊥ that is strong enough to position the plasma jet 180at a desirable distance along the apparatus axis 90.

Referring to FIG. 8, if the electrode 60 having axis 80 which isdirected with an angle α that is less than 45 degrees between thecorresponding electrode axis 80 and apparatus axis 90, then thedirections of electrical current in the coils 120 of both unclosedmagnetic circuit 110 are chosen to provide external magnetic fieldinduction vector components B₁⊥ and B₂⊥ that are directed perpendicularto the basic plane formed by the electrode axes 80 and the apparatusaxis 90, are oriented along the direction which is opposite to theorientation of corresponding plasma jet 180 self-magnetic fieldinduction vector B_(S) at the region of the basic plane between theelectrode axis 80 and apparatus axis 90. The external magnetic fieldinduction vector components B₁⊥ and B₂⊥ create electromagnetic forcesF₁⊥ and F₂⊥ correspondingly that are applied to the plasma jet 180 anddirected to the apparatus axis 90. The quantity of electrical currentsflowed through the coils 120 is chosen to provide compensation of theforce F_(S) by the sum of forces F₁⊥ and F₂⊥ to position the plasma jet180 at a desirable distance from the apparatus axis 90.

In both situations illustrated in FIGS. 7 and 8, due to the specificlocation of the pole ends 135, the external magnetic field inductionvector components B_(1//) and B_(2//), that are directed parallel to thebasic plane, are oriented in opposite directions. The external magneticfield induction vector components B_(1//) and B_(2//) createelectromagnetic forces F_(1//) and F_(2//) correspondingly that areapplied to the plasma jets 180, directed perpendicular to the basicplane and oriented in opposite directions. The value and direction ofthe resulting force is determined by the difference between the forcesF_(1//) and F_(2//). So the position of the plasma jet 180 relative tothe basic plane is changed by changing the quantity of electricalcurrents flowing in the coils 120.

When a combined plasma flow 200 is produced from two plasma jets 180 asillustrated in FIGS. 7 and 8, the quantity of electrical current flowingthrough coils 120 of the unclosed magnetic circuits 110 may be changedsynchronously so that the sum of the currents is kept constant. As aresult, the combined plasma flow 200 may be deflected from its initialdirection along apparatus axis 90 and oscillated in the planeperpendicular to the basic plane formed by the electrode axes 80 and theapparatus axis 90.

Referring to FIG. 1, According to the present invention, a substance 210for treating a substrate may be injected into the combined plasma flow.The substance is injected into the combined plasma flow 200 by directingthe substance at the mixing zone 190 with injection tube 150.

As will be understood from the foregoing description, according to thepresent invention, several embodiments of an apparatus for generatingand deflecting a plasma jet for treating substrates has been described.It is to be understood that the embodiments described herein are merelyillustrative of the principles of the invention. Various modificationsmay be made thereto by persons skilled in the art which will embody theprinciples of the invention and fall within the spirit and scopethereof. Hence, the present invention is deemed limited only by theappended claims and the reasonable interpretation thereof.

What is claimed is:
 1. A plasma generator (5) for generating anddeflecting a plasma jet comprising an electrode chamber (10) having agas inlet (50); and an outlet orafice (40); an electrode (60) positionedwithin the electrode chamber, the electrode defining an electrode axis(80); and a first magnetic deflection system for applying a firstmagnetic field (B1) to a plasma flowing from the electrode chamberoutlet so as to cause the plasma to flow away from the electrode axis ina first direction as a result of a first force (F1) on the plasma causedby the first magnetic field, the first magnetic deflection systemcomprising a first U-shaped member formed from a first base (110) and apair of first poles (130) having ends (135) and a first coil (120)positioned about the base, wherein the first magnetic deflection systemis positioned about the electrode chamber so that the poles of the pairof first poles are on opposite sides of the electrode axis defined bythe electrode positioned within the electrode chamber;the generatorbeing further characterized in that: the generator is provided with asecond magnetic deflection system for applying a second magnetic fieldto a plasma flowing from the electrode chamber outlet so as to cause theplasma to flow away from the electrode axis in a second direction as aresult of a second force (F2) on the plasma caused by the secondmagnetic field, the second magnetic deflection system comprising asecond U-shaped member formed from a second base (110) and a pair ofsecond poles (130) having ends (135) and a second coil (120) positionedabout the second base, wherein the second magnetic deflection system ispositioned about the electrode chamber so that the poles of the pair ofsecond poles are on opposite sides of the electrode axis defined by theelectrode positioned within the electrode chamber, and wherein the firstpair of poles and the second pair of poles are uniformly positionedabout the electrode axis so that the magnetic field across the firstpair of poles is substantially perpendicular to the magnetic fieldacross the pair of second poles.
 2. An apparatus for treating substrateswith a plasma jet, the apparatus comprising first and second plasma jetgenerator assemblies, each of the generator assemblies furthercomprising an electrode chamber (10) having a gas inlet (50) and anoutlet orafice (40), an electrode (60) positioned within the electrodechamber, the electrode defining an electrode axis (80), and a firstmagnetic deflection system for applying a first magnetic field to aplasma flowing from the electrode chamber outlet so as to cause theplasma to flow away from the electrode axis in a first direction as aresult of a first force (F1) on the plasma caused by the first magneticfield, the first magnetic deflection system comprising a first U-shapedmember formed from a first base (110) and a pair of first poles (130)having ends (135) and a first coil (120) positioned about the base,wherein the first magnetic deflection system is positioned about theelectrode chamber so that the poles of the pair of first poles are onopposite sides of the electrode axis defined by the electrode positionedwithin the electrode chamber;and an injection tube, defining anapparatus axis, positioned between the the generator assemblies; theapparatus being further characterized in that: each of the generatorassemblies are provided with a second magnetic deflection system forapplying a second magnetic field to a plasma flowing from the electrodechamber outlet so as to cause the plasma to flow away from the electrodeaxis in a second direction as a result of a second force (F2) on theplasma caused by the second magnetic field, the second magneticdeflection system comprising a second U-shaped member formed from asecond base (110) and a pair of second poles (130) having ends (135) anda second coil (120) positioned about the second base, wherein the secondmagnetic deflection system is positioned about the electrode chamber sothat the poles of the second pair of poles are on opposite sides of theelectrode axis defined by the electrode positioned within the electrodechamber, and wherein the poles of the first and second pairs of polesare positioned uniformly around the electrode axis so that the magneticfield across the first pair of poles is substantially perpendicular tothe magnetic field across the pair of second poles.
 3. The apparatusaccording to claim 2, wherein the first and second plasma jet generatorassemblies (5) are positioned with respect to the apparatus axis (90) soas to form a common plane between the electrode axes (40) of thegenerator assemblies and the apparatus axis, wherein generatorassemblies are further positioned such that the apparatus axis isbetween the respective electrode axes such that the electrode axes forman angle α with the apparatus axis, and such that the first and secondplasma jet generator assemblies are positioned sufficiently close toeach other to enable plasmas generated by each generator assembly toform a combined plasma flow having a mixing zone.
 4. The apparatusaccording to claim 3, wherein the angle α is greater than 45 degrees. 5.The apparatus according to claim 3, wherein the angle α is less than 45degrees.
 6. The apparatus according to claim 3, wherein the angle α is45 degrees.
 7. The apparatus according to claim 3, wherein the injectiontube has an oval shaped outlet, wherein the oval shaped outlet has along axis and a short axis, and wherein the long axis of the oval shapedoutlet is positioned substantially normal to the common plane.
 8. Theapparatus according to claim 3, wherein the injection tube has aplurality of outlets, and wherein the plurality of outlets are arrangedalong a line substantially normal to the common plane.